Range: Deep oceans worldwide

Habitat: Ocean floor

Size: 6 inch (15 cm) mantle length

Diet: Crustaceans and fish

Threats: Fish, seals, and belugas

Lifespan: At least two years

Transcript:

Today on Animal Fact Files we’re discussing the pearl octopus and its kin. These cephalopods are also called the smoothed skinned octopus for their unblemished mantle. The pearl octopus and its congeners are deep sea invertebrates. They are most often found more than 650 feet (200 m) below the ocean waves, and they can live far deeper. There are some individuals, however, that appear in water as shallow as 230 feet (70 m) and only recently have they been found in water merely 50 feet (15 m) deep where they can be accessed via scuba diving. Otherwise, it takes remote operated vehicles to study them alive in the wild.

It's not uncommon for other octopus species to show off defining features such as flaps of skin over the eyes, or Dumbo ear-like fins across the mantle. The pearl octopus, however, doesn't have these. As its other common name suggests, this octopus and its relatives are smooth-skinned. There are currently just over two dozen pearl or smooth-skinned octopus species, and their classification has a tumultuous history, so new information could help shed some light on these mysterious invertebrates of the abyss.

In general, a pearl octopus is orange to red in color with big eyes and eight arms equipped with paired sets of about 100 suction cups per arm. They have some webbing between their arms that reaches about a quarter of the way down their length. This animal's mantle averages about six inches (15 cm) long though females are slightly larger than their male counterparts. Males have a specialized arm for transferring sperm to the female's mantle cavity, and, similar to many octopus species, both parents perish after mating.

These invertebrates display unique behavior among all the known octopus species. At the depths these cephalopods live, the water temperature is near freezing. Typically, the colder the environment, the longer it takes for eggs to develop. The longer it takes for eggs to develop, the more time they're exposed to potential predators. Warmer temperatures often expedite the development process, and it's believed that a mother pearl octopus uses this phenomenon to promote faster development of her own eggs. Pearl octopus mothers gather in huge groups, the largest known gatherings of any octopus species. There may be thousands of mothers all seeking out the warmer waters of deep ocean hydrothermal springs.

Unlike hydrothermal vents that spew cloudy, heated water far above the ocean's floor, hydrothermal springs simply have heated water that seeps out from cracks in the ocean sediment. The pearl octopus mothers gather in droves asking these ocean bottom fissures where the temperature is warmer. Here, egg development that may have taken five to ten years, takes just under two, meaning the eggs are far less susceptible to predation. Plus, the mother octopus remains with her brood the entire time, splaying her arms in a defensive posture. 

Predators to the pearl octopus include skates and other large fish such as rockfish and dogfish, sea lions and fur seals, as well as beluga whales. In turn, the invertebrates eat crabs and other crustaceans as well as small fish. A mother pearl octopus doesn't eat while she protects her brood, and shortly after they've matured, she'll die. Her body, however, contributes to the organic cycle around the hydrothermal spring, so these habitats tend to be full of life!

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